| A collection of 47 black cherry genotypes was assembled from an orchard containing phenotypically superior ramets, and from select and average phenotypes growing in northwestern Pennsylvania. Seedlings were planted at three locations on the Allegheny National Forest, and treated with four rates of ammonium nitrate which encompassed the range needed to maintain maximum growth for four years. At two sites, nitrogen and selection effects were confounded by deer browsing and poor soil drainage.; Genotypic variation in height and diameter was found at all locations during the second year, but only height variations were affected by phenotypic selection of parent trees. At two locations, significant differences between orchard progeny and those of average phenotypes were evident but not consistent. However, these could not be interpreted in terms of the selection effect without ambiguity, as most of the average phenotypes were not representative of the same populations as the ortets of the orchard ramets. Height differences between progenies of superior and average phenotypes from the same stand were not significant at any location.; At the one location where height growth responded to nitrogen, significant genotype-by-fertilizer interaction effects were not detected. Neither were significant fertilizer interactions recorded at the other sites.; Interactions between genotypes and environments (the latter defined by the 12 location-nitrogen treatment combinations) were significant for both height and diameter. The interaction variance was modeled by regressing genotypic effects on environmental effects, but significant divergences in regression were not associated with the three groups of select and average progenies.; In a second analysis of genotype-by-environment interactions, the total interaction variance was partitioned among orthogonal comparisons of location and nitrogen effects. The analysis was effective in associating sets of genotypes with those environmental contrasts in which the genotype-by-environment interactions were maximized, and was determined to be a reliable way to stratify black cherry environments in selecting for optimum response patterns. Application of the orthogonal technique is discussed in regard to genotype-by-environment interactions and the specific sites which require artificial regeneration on the Allegheny Plateau. |
